The usage of the BIT() macro in asm code was introduced in 6.3 in by
commit 5d1dd961e743 ("x86/alternatives: Add alt_instr.flags") but this
macro uses "1UL" in the shift operations, while gas before 2.28 do not
support the "L" suffix after a number, and those before 2.27 do not
support the "U" suffix, resulting in build errors such as the following
with such versions:
./arch/x86/include/asm/uaccess_64.h:124: Error: found 'L', expected: ')'
./arch/x86/include/asm/uaccess_64.h:124: Error: junk at end of line,
first unrecognized character is `L'
There's a single use of this macro here, let's revert to (1 << 0) that
works with such older binutils.
Cc: Jingbo Xu <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Link: https://lore.kernel.org/lkml/[email protected]/
Signed-off-by: Willy Tarreau <[email protected]>
---
Boris, I understood from your message that 2.28 was the first working version,
so that's what I mentioned here. My tests showed that 2.27 wasn't sufficient
and that 2.29 was OK. If I was wrong and it's 2.29 instead, feel free to edit
the subject line, description and the comment, I'm totally fine with this!
arch/x86/include/asm/alternative.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index e2975a32d443..b119685c0b31 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -8,7 +8,7 @@
#define ALT_FLAGS_SHIFT 16
-#define ALT_FLAG_NOT BIT(0)
+#define ALT_FLAG_NOT (1 << 0) /* note: gas < 2.28 can't use BIT(0) */
#define ALT_NOT(feature) ((ALT_FLAG_NOT << ALT_FLAGS_SHIFT) | (feature))
#ifndef __ASSEMBLY__
--
2.35.3
On 4/18/23 2:42 PM, Willy Tarreau wrote:
> The usage of the BIT() macro in asm code was introduced in 6.3 in by
> commit 5d1dd961e743 ("x86/alternatives: Add alt_instr.flags") but this
> macro uses "1UL" in the shift operations, while gas before 2.28 do not
> support the "L" suffix after a number, and those before 2.27 do not
> support the "U" suffix, resulting in build errors such as the following
> with such versions:
>
> ./arch/x86/include/asm/uaccess_64.h:124: Error: found 'L', expected: ')'
> ./arch/x86/include/asm/uaccess_64.h:124: Error: junk at end of line,
> first unrecognized character is `L'
>
> There's a single use of this macro here, let's revert to (1 << 0) that
> works with such older binutils.
>
> Cc: Jingbo Xu <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: "H. Peter Anvin" <[email protected]>
> Link: https://lore.kernel.org/lkml/[email protected]/
> Signed-off-by: Willy Tarreau <[email protected]>
> ---
>
> Boris, I understood from your message that 2.28 was the first working version,
> so that's what I mentioned here. My tests showed that 2.27 wasn't sufficient
> and that 2.29 was OK. If I was wrong and it's 2.29 instead, feel free to edit
> the subject line, description and the comment, I'm totally fine with this!
>
>
> arch/x86/include/asm/alternative.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
> index e2975a32d443..b119685c0b31 100644
> --- a/arch/x86/include/asm/alternative.h
> +++ b/arch/x86/include/asm/alternative.h
> @@ -8,7 +8,7 @@
>
> #define ALT_FLAGS_SHIFT 16
>
> -#define ALT_FLAG_NOT BIT(0)
> +#define ALT_FLAG_NOT (1 << 0) /* note: gas < 2.28 can't use BIT(0) */
> #define ALT_NOT(feature) ((ALT_FLAG_NOT << ALT_FLAGS_SHIFT) | (feature))
>
> #ifndef __ASSEMBLY__
It works for me.
Tested-by: Jingbo Xu <[email protected]>
--
Thanks,
Jingbo
On Tue, Apr 18, 2023 at 08:42:28AM +0200, Willy Tarreau wrote:
> Boris, I understood from your message that 2.28 was the first working version,
> so that's what I mentioned here. My tests showed that 2.27 wasn't sufficient
> and that 2.29 was OK.
No, you have it right above:
U suffix - 2.27
L/LL suffixes - 2.28
I was wondering where to put that info for future reference but didn't
find a good place so I extended your commit message with it. Now at
least we have left bread crumbs in case we need it in the future.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
On Tue, Apr 18, 2023 at 12:02:12PM +0200, Borislav Petkov wrote:
> On Tue, Apr 18, 2023 at 08:42:28AM +0200, Willy Tarreau wrote:
> > Boris, I understood from your message that 2.28 was the first working version,
> > so that's what I mentioned here. My tests showed that 2.27 wasn't sufficient
> > and that 2.29 was OK.
>
> No, you have it right above:
>
> U suffix - 2.27
> L/LL suffixes - 2.28
>
> I was wondering where to put that info for future reference but didn't
> find a good place so I extended your commit message with it. Now at
> least we have left bread crumbs in case we need it in the future.
I wondered the same which is why I left it in the comment as a warning
for future wanderers.
Thanks!
Willy